Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$172.91	3.525%	$179.0051	$179.01	$179.00	$179.00
Purchase #2	$177.96	10.269%	$196.2347	$196.23	$196.25	$196.20
Purchase #3	$88.43	8.781%	$96.195	$96.20	$96.20	$96.20
Purchase #4	$144.42	11.674%	$161.2796	$161.28	$161.30	$161.30
Purchase #5	$195.39	11.377%	$217.6195	$217.62	$217.60	$217.60
Purchase #6	$218.73	7.702%	$235.5766	$235.58	$235.60	$235.60
Purchase #7	$173.47	3.456%	$179.4651	$179.47	$179.45	$179.50
7 purchase totals =	$1,171.31		$1,265.3756	$1,265.39	$1,265.40	$1,265.40